The performance of wireless cellular systems is significantly limited due to co-channel interference from neighboring base stations, especially as these systems move towards aggressive frequency reuse scenarios. While the overall spectral efficiency of the cellular system may improve with aggressive frequency reuse, the performance of cell-edge users degrades substantially. Recent research is focused on a variety of interference management techniques, ranging from the design of fractional frequency reuse (FFR) mechanisms for cell-edge users, to coordinated transmit beam-forming techniques, to receiver interference cancellation using multiple antennas.
One simple approach to reducing interference for the cell edge users is to reserve a set of frequencies used for transmission to only cell-edge users in a fashion such that adjacent cells use different sets of frequencies. This may be achieved through a fractional frequency reuse (FFR) mechanism wherein a lower frequency reuse is specified for users at the cell edge, cell-center users enjoy full frequency reuse. This improves the throughput performance of cell-edge users since they experience lower levels of interference.
FIG. 1 shows an exemplary network deployment 50 with fractional frequency reuse. Such a deployment enables most of the frequencies (‘white’) to be reused over a significant portion of each cell, and only a fraction of frequencies to be set aside for cell-edges (‘dotted’, ‘vertical striped’, ‘diagonal striped’). While initial deployments with FFR may use a static sub-division of cell-edge and cell-center frequencies, it is expected that the frequency reuse patterns be dynamically adjustable through coordination across the network, since the traffic load and user distribution may not be uniform across the network.